The Amateur Amateur: Putting It All Together (A Kitbuilding Saga)

By Gary Hoffman, KB0H
Contributing Editor
April 21, 2002

Kit-building
frustration is at the core of this month's adventure. A kit that I'd
hoped would nurture my wife's fledgling interest in the mechanics of
radio turned out to have just the opposite effect.

Did you have an
Erector Set when you were young? Perhaps you had a box of Tinker Toys
or Lincoln Logs. You may have moved on to building models when you
got older. Regardless of your sex, you probably had some toy
or toys that required that you put something together. When you put
these toys together, you undoubtedly learned something about how they
worked.

That is the idea
behind kits. You put the kit together and learn something about how
the finished product works. At least, that's the theory.

Nancy, my wife,
is actually the kit builder at our house. She feels that she can
learn more about radios when she can actually put one together. This
was one of her goals when she first got into Amateur Radio--to learn
how a radio works.

Not long after we
got our tickets, I bought Nancy three kits. I figured the first kit
would be easy, the second a bit more challenging and the third
somewhat difficult. Of course, I was subconsciously thinking how
difficult they would be for me. Now, I didn't really get into
electronics until I got my amateur license, but my father ran a radio
and television shop for many years, so I had some exposure to
it. Nancy, on the other hand, was unfamiliar with the tools and the
terminology. Her only exposure to the fundamentals of electronics and
radio was when she studied for her ham license.

The kits were
somewhat daunting, but she is a very determined person. I gave her a
tour of the workbench and a crash course in soldering. She opened kit
number one and started reading the instructions.

I must say that
Nancy had far fewer problems with the kit than I had expected. She
did ask me a few questions, and my answers tended to be along the
lines of, "Well, it's pretty obvious that . . . hmmmm! I guess
it's not all that obvious after all." If you've never handled a
diode, for example, it's not obvious which end is which (I'm still
not sure). The diagram that came with the kit showed where to place
the components on the board and marked which end was positive.
The actual components, however, were only marked at the negative
end. Well, sure. Intuition told us that the unmarked end of the
component was positive (likewise the unmarked end on the diagram was
negative), but why the heck weren't the diagram and components marked
the same way? I mean, give us a break!

We were new at
this and still full of insecurities. Instead of reassuring us, the
kit was making us doubt each decision.

Once you fudge the fudge factor, you end up way outside the margin of error.

Nancy finished her kit in a few days. It did not work. It was supposed to
pick up shortwave broadcasts. All we got by tuning across the band
was a lot of silence interspersed with an occasional Snap! Spit!
Blaaatt! That was enough for Nancy. She tossed the radio on the
workbench and left in frustration.

Not wanting to
see her first kit-building experience end on such a sour note, I
decided to check over her work. I spent about half an hour looking at
the radio and determined that Nancy had put the kit together
correctly. So why were we picking up Snap! Spit! Blaaatt!
instead of the BBC?

Well, this bugged
me. The kit that I'd hoped would nurture Nancy's fledgling interest
in the mechanics of radio instead had the opposite effect. I just had
to know why the radio didn't work (picking up Snap! Spit! Blaaatt!
didn't count).

I underwent a
transformation. Exit Gary, mild mannered programmer and husband, and
enter Compulsive Man! Lock the doors. Hide the children. The Insane
Avenger is here.

I read the kit's
instruction manual carefully. I didn't miss a single comma, period,
or hyphen. I compared each component with the parts list. I examined
each component and its placement on the circuit board. I checked
every solder joint. I squinted at everything through a magnifying
glass. I used a meter to check every part of the circuit. And
eventually, using my Amazing Compuls-o-Vision, I found out
what was wrong. The kit's manufacturer had supplied the cheapest,
most inferior components available.

No BBC, just Snap! Spit! Blaaatt!

Here is what
happened. Electronic components (resistors, capacitors, diodes and so
forth) are marked with the appropriate value. For example, a resistor
may tell you (in color code-ese, of course) "Hi there. I am a
100-ohm resistor."

But wait! There
is often another little color band (or no band at all) on the
component that indicates the tolerance, which might be 1, 5,
10, or even 20 percent. Good components will have a low tolerance.
So, let us assume that our sample resistor was marked to show that it
had a 10% tolerance. Its translated color code would tell you, "Hi
there. I am a 100-ohm resistor. But my tolerance is 10%, so I might
be a 90-ohm resistor, or I might be a 110-ohm resistor, or
anything in between. Ha-ha!"

Okay, store this
away while I move on to the next part of the explanation.

The kit's
instructions explained where to put each component ("Place a
250-ohm resistor here"). Even better, the instructions gave the
range of component value that could be used in a particular
spot. That is, for a particular place in the circuit, you didn't have
to use a 250-ohm resistor. You could use anything from a 240 to a
260-ohm resistor, and the radio should still work. Nice, eh?

Right. Now, here
is why the radio didn't work. First, many of the supplied components
had values that were not in the middle of the range of values
that could be used. They were on the edge of the values that
could be used. Second, virtually every component had an immensely
wide tolerance. So most of the components may have had values well
outside the useful range. For example, the instructions called
for 100-ohm resistor but said anything from 90 to 110 ohms would
suffice. The kit supplied a 110-ohm resistor, however--right on
the edge of the useful tolerance range.

What are the real values of these components?

Worse than
that, it had a 15% tolerance, which meant it might have a
value as high as 126.5 ohms, well outside of the useful range.
No wonder the blasted radio didn't work!

I went to an
electronics store and bought new components, all with much tighter
tolerances. I removed the kit-supplied components, put in the new
components, and sure enough, the radio started receiving shortwave
signals.

Let me reiterate
the purpose of kits. They are supposed to help you learn. Nancy
wanted to learn how radios work. What she learned instead was why
some radios don't work. Well, it was a lesson, but hardly a
satisfying one.

What I
learned is never to buy another kit from that particular
manufacturer.

Editor's
note: ARRL member Gary Hoffman, KB0H, lives in Florissant,
Missouri. He's been a ham since 1995. Hoffman says his column's
name-- "The Amateur Amateur"--suggests the explorations of
a rank amateur, not those of an experienced or knowledgeable ham. His
wife, Nancy, is N0NJ. Hoffman has a ham-related
Web page. Readers are invited to contact the
author via email.